CN114507339B - Preparation method of vanillin-based polyester - Google Patents

Abstract

The invention discloses a method for preparing vanillin-based polyester. The method comprises: preparing corresponding aldol monomer M1 from vanillin and halogenated alkyl alcohol, and generating corresponding diol monomer M1 under the action of a reducing agent M2; M1 and M2 monomers were dehydrogenated and condensed under the action of Milstein catalyst to generate bio-based polyesters containing aromatic groups, and the yield was higher than 90%. Compared with the traditional polycondensation, the process method of the present invention is easier to prepare the reaction monomer than the vanillic acid monomer, the reaction conditions are milder, the by-product is only hydrogen, the requirements for production equipment are low, and it is in line with the principles of green, efficient and safe production.

Description

A kind of preparation method of vanillin base polyester

technical field

The invention belongs to the technical field of bio-based polymer synthesis, and in particular relates to a preparation method of vanillin-based polyester.

Background technique

The use of fossil-based polymeric materials has an increasing impact on the environment. The so-called "white pollution" is formed by the refractory waste polymer materials accumulated year by year. At the same time, coal, petroleum, etc. are non-renewable resources, and extensive use will cause the exhaustion of fossil energy; moreover, the carbon dioxide emitted during the preparation of fossil-based polymer materials will also cause the "greenhouse effect". Based on the consideration of environmental protection and sustainable development, in recent years, the use of renewable resources to prepare bio-based polymer materials has attracted more and more attention.

Bio-based polyesters are one of the most important types of bio-based polymer materials. The currently commercialized bio-based polyesters polylactic acid (PLA), polyhydroxy fatty acid (PHA) and polybutylene succinate (PBS) ), etc. Although they have good biocompatibility and degradability, they are not compatible with traditional petroleum-based polyesters such as polyethylene terephthalate (PET), polybutylene terephthalate (PBT ), due to the lack of a rigid structure in the molecular chain, their performance in terms of strength, toughness, heat resistance, and gas barrier properties needs to be further improved. Therefore, there is an urgent need to develop a method for the preparation of bio-based polyesters containing rigid groups.

Vanillic acid (VA) derived from biomass has become one of the candidate compounds for aromatic-based monomers, which can be used to prepare fully bio-based or partially bio-based polyesters. So far, there have been more and more studies on VA polyesters, but the synthesis process needs to convert vanillin into corresponding hydroxy acids, and then further polycondensate to obtain vanillic acid-based polyesters; and this polycondensation reaction requires high temperature or even vacuum It is carried out under harsh conditions such as high energy consumption, and the molecular weight of the obtained polymer is low, and the molecular weight distribution is uncontrollable. Therefore, it is urgent to develop a new polymerization method to realize the polymerization of vanillin monomers under mild conditions to synthesize aromatic polyesters.

In 2005 and 2007, Israeli scientist Milstein's research group used pincer ruthenium complexes (PNN-Ru) as catalysts to realize the dehydrogenation coupling of alcohols to generate esters, and the dehydrogenation coupling of alcohols and amines to generate amides, with high catalytic efficiency and The only by-product is hydrogen. These two types of reactions provide an opportunity for the efficient dehydrogenation and polycondensation of alcohols to prepare polyesters and polyamides. In 2011, the American scientist Guan's research group applied Milstein's catalytic system to realize the direct dehydrogenation polycondensation of diols and diamines and successfully prepared polyamides. In 2012, Milstein's research group also conducted research on this reaction and further expanded the types of reaction substrates. In the same year, Robertson's research group applied this catalytic system to realize the bulk dehydrogenation polycondensation of long-chain diols to obtain polyesters, and the number-average molecular weight of the obtained polymers can reach up to 145kg/mol. The mechanism of the two types of dehydrogenation condensation reactions is shown in Fig. 1: the alcohol reacts with the pyridyl ring dearomatized PNN-Ru complex to generate the pyridyl ring re-aromatized Ru-OR intermediate, which is eliminated by eliminating the alkoxy group α -The hydrogen on the carbon atom obtains the ruthenium dihydrogen compound of pyridine ring aromatization, and simultaneously releases a molecule of aldehyde; and the unstable ruthenium dihydrogen compound obtains a catalyst for dearomatization of pyridine ring by removing a molecule H ₂ ( Process A). The generated aldehyde reacts with alcohol or amine to generate hemiacetal or hemiaminal (process B), and the newly generated hydroxyl group further reacts with the catalyst to finally generate ester or amide (process C). This is a new type of metal-ligand synergistically catalyzed reaction. It can be seen from Figure 1 that in the entire catalytic process, in addition to the central metal, the ligand coordinated with it also participates in the activation process of the reaction substrate. Compared with traditional homogeneous catalysis, "metal-ligand synergistic" catalysis significantly expands the range of catalytic reactions and promotes the birth of many environmentally friendly catalytic reactions, such as: the catalysis of polar unsaturated groups under mild conditions Hydrogenation, acceptor-free dehydrogenation, etc. These catalytic reactions are of great significance both in organic synthesis and in the development of alternatives to petrochemical energy.

In view of this, the present invention hopes to further apply this kind of catalytic reaction to the dehydrogenation polycondensation of biomass monomer vanillin derivatives, and to prepare biodegradable polyester materials with different structural properties.

Contents of the invention

In order to solve the shortcomings of existing aliphatic polyesters such as poor strength, toughness, heat resistance, and gas barrier properties, as well as the harsh polymerization conditions, the present invention provides a method for preparing a series of methods for aromatic-based polyesters. This method can use aldol derivatives or diol derivatives of vanillin as raw materials to efficiently prepare aromatic-based bio-based polyesters under mild conditions; at the same time, it does not need to convert vanillin into vanillic acid, and the by-product is only hydrogen. So the response is more green economy.

The present invention is specifically achieved through the following technical solutions:

A preparation method of vanillin-based polyester, carried out as follows:

1) Preparation of vanillin monomer: react vanillin with halogenated alkyl alcohol to generate monomer M1 containing aldehyde group and hydroxyl group, and reduce the aldehyde group of monomer M1 to prepare monomer M2 containing double hydroxyl group;

The preparation method of described vanillin monomer is as follows:

2) Preparation of vanillin-based biodegradable polyester: Dissolve Milstein catalyst in an organic solvent to prepare a catalytic system, then add the monomer M1 or M2 prepared in step 1), heat the monomer to polymerize, and obtain vanillin-based biodegradable polyester Degradable polyester.

Preferably, X in the halogenated alkyl alcohol in step 1) is selected from any one of chlorine, bromine and iodine.

Preferably, R in the halogenated alkyl alcohol in step 1) is a straight chain alkane, a branched alkane or an alkane containing unsaturated bonds or heteroatoms with a chain length of 1-11.

Preferably, the haloalkyl alcohol is selected from 4-chloro-1-butanol, 5-chloro-1-pentanol, 6-chloro-1-hexanol, 7-chloro-1-heptanol, 8-chloro- 1-octanol, 9-chloro-1-nonanol, 10-chloro-1-decanol, 2-bromoethanol, 3-bromo-1-propanol, 4-bromo-1-butanol, 5-bromo- 1-pentanol, 6-bromo-1-hexanol, 7-bromo-1-heptanol, 8-bromo-1-octanol, 9-bromo-1-nonanol, 10-bromo-1-decanol, 11-bromo-1-undecanol, 12-bromo-1-dodecanol, 2-iodoethanol, 3-iodo-1-propanol, 4-iodo-1-butanol, 5-iodo-1- Pentanol, 6-iodo-1-hexanol, 7-iodo-1-heptanol, 8-iodo-1-octanol, 9-iodo-1-nonanol, 10-iodo-1-decanol.

Preferably, the ratio of the vanillin monomer M1 or M2 to the catalyst in step 2) is (50-5000):1 (concentration ratio).

Preferably, the polymerization temperature in step 2) is 80-180° C., and the polymerization reaction time is 1-5 days.

In the present invention, the aldehyde group of the aldol monomer M1 and the hydroxyl group are dehydrogenated to form an ester bond, or the diol monomer is dehydrogenated and condensed twice to form an ester bond. The polymerization method is novel; by adjusting the carbon chain length of the halogenated alkyl alcohol, thereby adjusting The nature of the polymer; due to the different regioselectivity during polymerization, the chain structure of the resulting polyester is more diverse, and its properties are quite different from those of vanillic acid-based polyesters.

Vanillin-based polyester is a very useful polymer and is expected to replace the traditional petroleum-based polyester PET and its derivatives; the raw material vanillin is derived from lignin and has been industrialized. The invention has relatively mild reaction conditions, simple process operation, easy separation of polymers, recyclable solvent, and avoids environmental problems brought about in the process.

Compared with prior art, the beneficial effect of the present invention is:

(1) Vanillin is derived from biomass, and the preparation of biodegradable polyester from its derivatives is simple, avoids environmental problems caused by the preparation process and polymer use, and realizes efficient utilization of resources.

(2) The present invention does not need to convert vanillin into vanillic acid, the reaction conditions are milder than traditional polycondensation, the requirements for production equipment are not high, and the principle of safe production is met.

(3) The present invention uses a metal catalyst that is more energy-saving and environment-friendly, so that the entire polymerization process only produces the target polymer and hydrogen, while hydrogen can be used as a clean energy source, and the product is easy to separate and purify, and has very large potential industrial applications.

Description of drawings

Figure 1 shows the reaction mechanism of "metal-ligand synergistic" catalyzed dehydrogenation condensation of alcohols to produce esters or amides.

Figure 2 is the H NMR spectrum of M1-C10 and M2-C10.

Fig. 3 is the H NMR spectrum of polyester prepared by using M2-C10 as monomer.

Detailed ways

In order to make the object, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in conjunction with embodiments. Those who do not indicate the specific conditions in the examples are carried out according to the conventional conditions or the conditions suggested by the manufacturer. The reagents or instruments used were not indicated by the manufacturer, and they were all conventional products that could be purchased from the market.

Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the technical field of the invention. The terms used in the description of the present invention are only for the purpose of describing specific embodiments, and are not used to limit the present invention. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.

Example 1

Synthesis of 4-(2-hydroxyethoxy)-3-methoxybenzaldehyde: add 0.1mol vanillin and 200mL acetonitrile into a 500mL reaction flask, stir to dissolve completely, then add 0.2mol anhydrous potassium carbonate, Stir at room temperature for 30 minutes, add 0.3 mol of 2-bromoethanol, stir and reflux for 16 hours. The reaction was stopped, the temperature was lowered to room temperature, filtered, purified by column chromatography and the yield was calculated. NMR and mass spectrometry confirmed its structure.

Example 2

Synthesis of 4-(3-hydroxypropoxy)-3-methoxybenzaldehyde: Add 0.1mol vanillin and 200mL acetonitrile into a 500mL reaction flask, stir to dissolve completely, then add 0.2mol anhydrous potassium carbonate, Stir at room temperature for 30 minutes, add 0.3mol 3-bromopropanol, and stir and reflux for 16 hours. The reaction was stopped, the temperature was lowered to room temperature, filtered, purified by column chromatography and the yield was calculated. NMR and mass spectrometry confirmed its structure.

Example 3

Synthesis of 4-(4-hydroxybutoxy)-3-methoxybenzaldehyde: Add 0.1mol vanillin and 200mL acetonitrile into a 500mL reaction flask, stir to dissolve completely, then add 0.2mol anhydrous potassium carbonate, Stir at room temperature for 30 minutes, add 0.3mol 4-bromobutanol, and stir and reflux for 16 hours. The reaction was stopped, the temperature was lowered to room temperature, filtered, purified by column chromatography and the yield was calculated. NMR and mass spectrometry confirmed its structure.

Example 4

Synthesis of 4-(5-hydroxypentyloxy)-3-methoxybenzaldehyde: Add 0.1mol vanillin and 200mL acetonitrile into a 500mL reaction flask, stir to dissolve completely, then add 0.2mol anhydrous potassium carbonate, Stir at room temperature for 30 minutes, add 0.3 mol of 5-bromopentanol, and stir under reflux for 16 hours. The reaction was stopped, the temperature was lowered to room temperature, filtered, purified by column chromatography and the yield was calculated. NMR and mass spectrometry confirmed its structure.

Example 5

Synthesis of 4-(6-hydroxyhexyloxy)-3-methoxybenzaldehyde: Add 0.1mol vanillin and 200mL acetonitrile into a 500mL reaction flask, stir to dissolve completely, then add 0.2mol anhydrous potassium carbonate, Stir at room temperature for 30 minutes, add 0.3 mol of 6-bromohexanol, and stir under reflux for 16 hours. The reaction was stopped, the temperature was lowered to room temperature, filtered, purified by column chromatography and the yield was calculated. NMR and mass spectrometry confirmed its structure.

Example 6

Synthesis of 4-(7-hydroxyheptyloxy)-3-methoxybenzaldehyde: Add 0.1mol vanillin and 200mL acetonitrile into a 500mL reaction flask, stir to dissolve completely, then add 0.2mol anhydrous potassium carbonate, Stir at room temperature for 30 minutes, add 0.3 mol of 7-bromoheptanol, and stir under reflux for 16 hours. The reaction was stopped, the temperature was lowered to room temperature, filtered, purified by column chromatography and the yield was calculated. NMR and mass spectrometry confirmed its structure.

Example 7

Synthesis of 4-(8-hydroxyoctyloxy)-3-methoxybenzaldehyde: Add 0.1mol vanillin and 200mL acetonitrile into a 500mL reaction flask, stir to dissolve completely, then add 0.2mol anhydrous potassium carbonate, Stir at room temperature for 30 minutes, add 0.3 mol of 8-bromooctyl alcohol, and stir under reflux for 16 hours. The reaction was stopped, the temperature was lowered to room temperature, filtered, purified by column chromatography and the yield was calculated. NMR and mass spectrometry confirmed its structure.

Example 8

Synthesis of 4-(9-hydroxynonyloxy)-3-methoxybenzaldehyde: Add 0.1mol vanillin and 200mL acetonitrile into a 500mL reaction flask, stir to dissolve completely, then add 0.2mol anhydrous potassium carbonate, Stir at room temperature for 30 minutes, add 0.3mol 9-bromononanol, and stir and reflux for 16 hours. The reaction was stopped, the temperature was lowered to room temperature, filtered, purified by column chromatography and the yield was calculated. NMR and mass spectrometry confirmed its structure.

Example 9

Synthesis of 4-(10-hydroxydecyloxy)-3-methoxybenzaldehyde: Add 0.1mol vanillin and 200mL acetonitrile into a 500mL reaction flask, stir to dissolve completely, then add 0.2mol anhydrous potassium carbonate, Stir at room temperature for 30 minutes, add 0.3 mol of 10-bromodecyl alcohol, stir and reflux for 16 hours. The reaction was stopped, the temperature was lowered to room temperature, filtered, purified by column chromatography and the yield was calculated. NMR and mass spectrometry confirmed its structure.

Example 10

Synthesis of 4-(2-hydroxyethoxy)-3-methoxybenzyl alcohol: Add 0.05 mol of 4-(2-hydroxyethoxy)-3-methoxybenzaldehyde in a 500mL reaction flask in methanol ( 300mL), and then slowly add 0.1mol sodium borohydride in an ice-water bath. After the addition, the ice-water bath was removed, and the reaction was stirred at room temperature for 5 hours. Stop the reaction, filter, purify by column chromatography and calculate the yield. NMR and mass spectrometry confirmed its structure.

Example 11

Synthesis of 4-(3-hydroxypropoxy)-3-methoxybenzyl alcohol: Add 0.05 mol of 4-(3-hydroxypropoxy)-3-methoxybenzaldehyde in methanol solution ( 300mL), and then slowly add 0.1mol sodium borohydride in an ice-water bath. After the addition, the ice-water bath was removed, and the reaction was stirred at room temperature for 5 hours. Stop the reaction, filter, purify by column chromatography and calculate the yield. NMR and mass spectrometry confirmed its structure.

Example 12

Synthesis of 4-(4-hydroxybutoxy)-3-methoxybenzyl alcohol: add 0.05mol of 4-(4-hydroxybutoxy)-3-methoxybenzaldehyde methanol solution in a 500mL reaction flask ( 300mL), and then slowly add 0.1mol sodium borohydride in an ice-water bath. After the addition, the ice-water bath was removed, and the reaction was stirred at room temperature for 5 hours. Stop the reaction, filter, purify by column chromatography and calculate the yield. NMR and mass spectrometry confirmed its structure.

Example 13

Synthesis of 4-(5-hydroxypentyloxy)-3-methoxybenzyl alcohol: Add 0.05 mol of 4-(5-hydroxypentyloxy)-3-methoxybenzaldehyde in a 500mL reaction flask in methanol ( 300mL), and then slowly add 0.1mol sodium borohydride in an ice-water bath. After the addition, the ice-water bath was removed, and the reaction was stirred at room temperature for 5 hours. Stop the reaction, filter, purify by column chromatography and calculate the yield. NMR and mass spectrometry confirmed its structure.

Example 14

Synthesis of 4-(6-hydroxyhexyloxy)-3-methoxybenzyl alcohol: add 0.05mol 4-(6-hydroxyhexyloxy)-3-methoxybenzaldehyde methanol solution in a 500mL reaction flask ( 300mL), and then slowly add 0.1mol sodium borohydride in an ice-water bath. After the addition, the ice-water bath was removed, and the reaction was stirred at room temperature for 5 hours. Stop the reaction, filter, purify by column chromatography and calculate the yield. NMR and mass spectrometry confirmed its structure.

Example 15

Synthesis of 4-(7-hydroxyheptyloxy)-3-methoxybenzyl alcohol: add 0.05 mol of 4-(7-hydroxyheptyloxy)-3-methoxybenzaldehyde in a 500mL reaction flask in methanol ( 300mL), and then slowly add 0.1mol sodium borohydride in an ice-water bath. After the addition, the ice-water bath was removed, and the reaction was stirred at room temperature for 5 hours. Stop the reaction, filter, purify by column chromatography and calculate the yield. NMR and mass spectrometry confirmed its structure.

Example 16

Synthesis of 4-(8-hydroxyoctyloxy)-3-methoxybenzyl alcohol: Add 0.05 mol of 4-(8-hydroxyoctyloxy)-3-methoxybenzaldehyde in a 500mL reaction flask in methanol ( 300mL), and then slowly add 0.1mol sodium borohydride in an ice-water bath. After the addition, the ice-water bath was removed, and the reaction was stirred at room temperature for 5 hours. Stop the reaction, filter, purify by column chromatography and calculate the yield. NMR and mass spectrometry confirmed its structure.

Example 17

Synthesis of 4-(9-hydroxynonyloxy)-3-methoxybenzyl alcohol: Add 0.05 mol of 4-(9-hydroxynonyloxy)-3-methoxybenzaldehyde in a 500mL reaction flask in methanol ( 300mL), and then slowly add 0.1mol sodium borohydride in an ice-water bath. After the addition, the ice-water bath was removed, and the reaction was stirred at room temperature for 5 hours. Stop the reaction, filter, purify by column chromatography and calculate the yield. NMR and mass spectrometry confirmed its structure.

Example 18

Synthesis of 4-(10-hydroxydecyloxy)-3-methoxybenzyl alcohol: Add 0.05 mol of 4-(10-hydroxydecyloxy)-3-methoxybenzaldehyde in a 500mL reaction flask in methanol ( 300mL), and then slowly add 0.1mol sodium borohydride in an ice-water bath. After the addition, the ice-water bath was removed, and the reaction was stirred at room temperature for 5 hours. Stop the reaction, filter, purify by column chromatography and calculate the yield. NMR and mass spectrometry confirmed its structure.

Embodiment 19 (polymer synthesis method)

In a glove box, Milstein catalyst (9.8 mg, 0.02 mmol) and potassium tert-butoxide (2.2 mg, 0.02 mmol) were added to a 25 mL reaction vessel, followed by toluene or anisole (1.0 mL), and the mixture was stirred at room temperature The catalyst was activated by stirring for 5 minutes. Then add monomer M1 or M2 (1 mmol, take this amount as an example), seal the container, transfer it out of the glove box, and heat the solution to 120°C with stirring in an oil bath. The reaction was stirred under nitrogen atmosphere for 12 hours, then the solvent was removed under reduced pressure and the reaction was carried out under vacuum for 4 days. After cooling to room temperature, the reaction vessel was removed from the oil bath, and the resulting polymer was dissolved in a small amount of toluene and then precipitated into methanol. The dissolution-precipitation was repeated three times, and the polymer was vacuum-dried. The polymer was characterized by NMR, GPC, DSC, and TGA.

Table 1 Vanillin-based monomers M1 and M2 generate polyester data under the action of catalysts

Remarks: M1 is an aldol monomer; M2 is a diol monomer; C2~C12 represent the number of carbon atoms connected to an alkyl alcohol.

The above-described embodiments only express several preferred embodiments of the present invention, and the descriptions thereof are more specific and detailed, but are not intended to limit the present invention. It should be pointed out that for those skilled in the art, the present invention can also have various changes and modifications, and any modifications, equivalent replacements, improvements, etc. within the concept and principles of the present invention should be included in the within the protection scope of the present invention.

Claims (5)

1. a preparation method of vanillin-based polyester, characterized in that, proceed as follows: 1) Preparation of vanillin monomer: react vanillin with halogenated alkyl alcohol to generate monomer M1 containing aldehyde group and hydroxyl group; The preparation method of described vanillin monomer is as follows: ; R in the halogenated alkyl alcohol is a straight-chain alkane, a branched alkane or an alkane containing unsaturated bonds or heteroatoms with a chain length of 1-11; 2) Preparation of vanillin-based biodegradable polyester: dissolving Milstein catalyst in an organic solvent to prepare a catalytic system, then adding the monomer M1 prepared in step 1), and heating to polymerize the monomer to obtain vanillin-based biodegradable polyester. 2. The method for preparing a vanillin-based polyester according to claim 1, wherein X in the halogenated alkyl alcohol in step 1) is selected from any one of chlorine, bromine, and iodine. 3. the preparation method of a kind of vanillin-based polyester according to claim 1, is characterized in that, described halogenated alkyl alcohol is selected from 4-chloro-1-butanol, 5-chloro-1-pentanol, 6- Chloro-1-hexanol, 7-chloro-1-heptanol, 8-chloro-1-octanol, 9-chloro-1-nonanol, 10-chloro-1-decanol, 2-bromoethanol, 3- Bromo-1-propanol, 4-bromo-1-butanol, 5-bromo-1-pentanol, 6-bromo-1-hexanol, 7-bromo-1-heptanol, 8-bromo-1-octyl alcohol alcohol, 9-bromo-1-nonanol, 10-bromo-1-decanol, 11-bromo-1-undecanol, 12-bromo-1-dodecanol, 2-iodoethanol, 3-iodo- 1-propanol, 4-iodo-1-butanol, 5-iodo-1-pentanol, 6-iodo-1-hexanol, 7-iodo-1-heptanol, 8-iodo-1-octanol, 9-iodo-1-nonanol, 10-iodo-1-decanol. 4 . The method for preparing a vanillin-based polyester according to claim 1 , wherein the ratio of the vanillin monomer M1 to the catalyst in step 2) is (50-5000):1. 5 . The method for preparing a vanillin-based polyester according to claim 1 , wherein the polymerization temperature in step 2) is 80-180° C., and the polymerization reaction time is 1-5 days.

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